+ TESTING openarc.org provides infrastructure you may use to get familar with ARC. ++ 1. Autoresponder Send a message to echo@openarc.org. You'll receive a response seconds later. This response contain the message as received by the service. This allowes you to inspect how !OpenARC validate your sent message. ++ 2. Forwarder Send a message to forward@openarc.org. You'll receive your message //forwarded// back to you seconds later. It's not a new one. Existing DKIM signatures are expected to be still intact after forwarding. But you may force message modification to invalidate your existing DKIM signature: Choose the text "modify" as Subject and it will be prepended with "[MODIFIED]: " on forwarding. Your DKIM signature will be no longer valid. We assume you sign the RFC5322.Subject header as advised by [https://tools.ietf.org/html/rfc6376#section-5.4 RFC 6376 - DKIM Signatures] You may also choose the text "add" as Subject and it will add a second Subject header into your message. That way you could see DKIM signatures stay valid unless yoiu use oversigning. [http://noxxi.de/research/breaking-dkim-on-purpose-and-by-chance.html Background] and [https://tools.ietf.org/html/rfc6376#section-8.15 DKIM SPEC] ++ 3. Mailing-List [mailto:openarc-testing+subscribe@openarc.org Subscribe] to the mailing list first. Then you may send messages to openarc-testing@openarc.org. As usual your message is resend to all subscriber. There is no public list archive as that donsn't make sense.